Overturning a 1-2 scoreline from the first leg, Craig Shakespeare's men created history at the Kingpower Stadium.
In another match, Juventus ousted FC Porto out of the tournament by beating them 1-0 (3-0 on aggregate) to qualify for the next round.
On Thursday, March 16, Monaco pumped in 3 goals against Manchester City to overturn a 3-5 defeat from first leg to qualify for the lats 8 stage.
The aggregate score was 6-6 but by virtue of 3 away goals scored in the first leg, the French side got better of Pep Guardiola's side.
In another match on Thursday, Atletico Madrid managed a goalless draw to qualify 4-2 on aggregate.
Here are some photos from UCL round of 16 second leg game week 2
Leicester City lone flag-bearer of England in UCL
Leicester City created by qualifying for the Champions League quarter-final for the first time in their history.
AS Monaco players celebrate (Image courtesy: Monaco Twitter handle)
As Monaco overturned a 3-5 deficit from the first leg to beat Manchester City 3-1 in the 2nd leg to qualify for the quarter-final.
Leroy Sane (right) against Monaco (Image courtesy: Manchester City Twitter handle)
Leroy Sane scored the only goal for Manchester City in the round of 16 second leg clash against Monaco.
Juventus players celebrate (Image courtesy: Juventus Twitter handle)
Juventus eased past FC Porto to qualify for the quarter-final yet again.
Atletico Madrid Vs Bayer Leverkusen (Image courtesy: Atletico Madrid Twitter handle)
Atletico Madrid managed a 0-0 draw against Bayer Leverkusen to qualify for the quarter-final for the sixth consecutive time.